Situation of Ralstonia solanacearum in Guatemala
The diversity and distribution of Ralstonia solanacearum (EPPO A2 List) strains was studied in Guatemala. In 2004 and 2005, 59 strains were isolated from different regions and from different crops: banana (Musa spp.), solanaceous plants (Lycopersicon esculentum, Solanum americanum, S. melongena, S. tuberosum), and Pelargonium. These isolates were characterized using physiological and molecular tests to place the strains within the biovar and the phylotype/sequevar classification systems. Results showed that three distinct types of R. solanacearum were present in Guatemala:
1) phylotype I, sequevar 14, strains infecting S. americanum, tomatoes and aubergines in areas located at moderate elevations (100-1000 m altitude);
2) phylotype II, sequevar 6 (race 2), strains causing Moko disease in lowland banana plantations (departments of Escuintla, Izabal, Quetzaltenango, and San Marcos);
3) phylotype II, sequevar 1 (race 3 biovar 2), strains causing brown rot of potatoes, Southern wilt of Pelargonium (1 sample from Guatemala province) and bacterial wilt of glasshouse tomatoes at high elevations. On tomatoes, R. solanacearum was detected in samples from Chiquimula, and Guatemala provinces. It is noted that tomato growers had noticed that tomato wilt was becoming a problem during the last decade in the highlands. On potatoes, R. solanacearum was found in the provinces of Baja Verapaz, Chimaltenango, Jalapa, Quetazltenango, and Sololá.
This study confirms that R. solanacearum occurs in Guatemala and is causing problems in banana, tomato and potato cultivation.
Another aspect of this study was to determine if tomato fruits from naturally infected plants contained detectable bacteria and could disseminate R. solanacearum. So far, the bacterium has been isolated only from roots, stems, tubers and leaves of infected plants. A sensitive enrichment method (using CIPEB medium) did not detect the pathogen in fruits from naturally infected commercial tomato plants but could detect R. solanacearum in 6% of fruits from a wilt-resistant experimental hybrid. Despite the rareness of fruits containing the bacterium, it is noted that these results indicate that the pathogen is able to move from the vascular system of the plant to the fruit under some circumstances which remain to be explained.
Sanchez Perez A, Mejia L, Fegan M, Allen C (2008) Diversity and distribution of Ralstonia solanacearum strains in Guatemala and rare occurrence of tomato fruit infection. Plant Pathology 57(2), 320-331.